Monotonic torsional resistance and fatigue resistance of novel SCOPE RS instruments

Evaluation of Cyclic Fatigue Resistance of Novel Replica-Like Instruments in Static Test Model

Introduction

The aim of our study is to comparatively analyze the canal cyclic fatigue resistance of widely used rotary file systems, including EndoArt Touch Gold (ETG), Perfect MTF Plus Gold (PPG), Fanta V-Taper Gold (FVG), and ProTaper Next (PTN).

Methods

Stainless steel canals with a 60° angle and a 3-mm curvature radius were specially prepared. The canals were shaped with each rotary file system and tested for resistance using a cyclic fatigue testing apparatus. The number of fracture cycles (NFC; K file tip separation) was measured. Data were analysed by one-way ANOVA and post hoc LSD tests.

Results

PTN and PPG rotary file systems exhibited the highest NFC. The NFC value for PTN was 589 ± 63, and for PPG, it was 507 ± 51.

Conclusion

The results of this study demonstrate that rotary file systems such as PTN and PPG exhibit higher cyclic fatigue resistance. ETG and FVG rotary file systems also possess generally acceptable cyclic fatigue resistance levels.

Nickel ion release and surface analyses on instrument fragments fractured beyond the apex: a laboratory investigation

BACKGROUND

To analyse the changes in surface and nickel ion release characteristics of fractured root canal shaping instruments in a simulated body fluid environment.

METHODS

A total of 54 new instruments were studied. The instrument groups consisted of five different NiTi alloys and a stainless-steel alloy. To standardize instrument fracture, a torsional type of failure was created on each instrument. The fractured specimens of each instrument group were randomly divided into three static immersion subgroups of 1 h, 7-day, and 30-day (n = 3). Simulated body fluid (SBF) was prepared to mimic human blood plasma by Kokubo&Takadama protocol for ex situ static immersions at 37ºC. The surfaces were examined via scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy. To determine the quantitative ion release, the retrieved SBFs were analyzed using inductively coupled plasma mass spectrometry. Two-way ANOVA and Tukey post hoc tests sought the statistical significance of the nickel ion values(p < 0.05).

RESULTS

In 1 h of immersion, the newly formed structures, exhibiting mostly oxygen signals, were widespread and evident on NiTi surfaces. In contrast, fewer structures were detected on the SS surface in that subgroup. In 7 days of immersion, a tendency for a decrease in the density of the new structures was revealed in NiTi groups. The oxygen signals on NiTi group surfaces significantly increased, contrary to their decrease in SS. Signals of sodium, chlorine, and calcium were detected, indicating salt precipitates in groups. In 30 days of immersion, salt precipitates continued to form. The Ni-ion release values in all instrument groups presented significant differences in comparison to the SBF control in all immersion periods(p < 0.001). No significant differences were observed in immersion time periods or instrument groups(p > 0.05).

CONCLUSIONS

Within the limitations of the presented study, it was concluded that the fractured SS and NiTi root canal instruments release Ni ions in contact with body fluid. However, the Ni ion release values determined during the observation periods are lower than the critical toxic or allergic thresholds defined for the human body. This was due to the ionic dissolution cycle reaching a stable state from 1-hour to 30-day exposure to the body fluid of fractured instruments.

Mechanical performance and Metallurgical Characteristic of Five Different Single-File Reciprocating Instruments: a Comparative in Vitro and Laboratory Study

INTRODUCTION

Since there are no data regarding an instrument recently introduced on the market (OneRECI), the aim of the study was to assess its mechanical and metallurgical properties comparing them with those of widespread reciprocating instruments such as Reciproc, Reciproc Blue, EdgeOne Fire and WaveOne Gold.

METHODS

A total of 65 NiTi files from five different reciprocating systems (OneRECI, Reciproc, Reciproc Blue, EdgeOne Fire and WaveOne Gold) were evaluated throughout a combined mechanical and metallurgical method. Mechanical performances of the selected file were examined subjecting each specimen to cyclic fatigue, torsional and bending resistance tests, whilst their metallurgical properties were assessed analyzing the nickel-titanium alloy composition and the phase transformation temperatures respectively through an energy-dispersive X-ray spectroscopy (EDX) and a differential scanning calorimetry (DSC). One-way ANOVA and post hoc Tukey's was performed with significance level set to a 95% confidence level.

RESULTS

The EDX showed a similar alloy composition for all of the tested files, with nickel percentage of about 52-53% and a corresponding percentage of titanium of 47-48%, whilst the DSC analysis, although evidenced martensitic characteristics for all files, showed differences in terms of phase transformation temperatures. Overall, OneRECI showed the best mechanical performances in terms of cyclic fatigue and torsional resistance (respectively of 32.95 ± 2.33 s and 0.76 ± 0.03 Ncm) and flexibility (48.4 ± 4.1 g), with statistically significant differences for all tests (p<0.05). Reciproc files showed the worst flexibility and cyclic fatigue resistance, respectively of 157.2 ± 8.3 g and 9.27 ± 1.18 s, whilst the EdgeOne Fire showed the lowest torsional resistance (0.39 ± 0.12 Ncm), whit statistically significant differences (p<0.05).

CONCLUSIONS

Within the limitation of this study, the recently introduced file OneRECI showed the best mechanical performance in comparison to the tested instruments, with an equiatomic composition of the NiTi alloy and a martensitic behavior.

Comparison of the Torsional Resistance of 4 Different Glide Path Instruments

INTRODUCTION

The present study aimed to compare the torsional strength of the initial files of the Mtwo (VDW, Munich, Germany) and novel Rotate systems (VDW, Munich, Germany) with the ProGlider (Dentsply Sirona, Ballaigues, Switzerland) and R-Pilot (VDW) glide path instruments.

METHODS

The Mtwo (10/.04), ProGlider (16/.02), R-Pilot (12.5/.04), and Rotate (15/.04) glide path files were compared regarding their torsional strength, which was tested using a specially designed test device (N = 20). The data obtained were statistically analyzed at 5% significance level using 1-way analysis of variance and the post hoc Tukey test. The fragment surfaces and separated instruments were examined with ×50, ×100, and ×1000 magnification under a scanning electron microscope.

RESULTS

The R-Pilot group showed the highest torsional strength value among all groups (P < .05), whereas there was no significant difference between the torsional strength values of the Mtwo and ProGlider groups (P > .05). The Rotate group had the lowest torsional strength among all groups (P < .05). The Mtwo group showed the lowest angle of rotation among all groups (P < .05).

CONCLUSIONS

Although the R-Pilot glide path file exhibited the highest torsional strength in all groups, Rotate showed the highest angle of rotation. Differences in torsional resistance of the instruments may be associated with their manufacturing methods and design features.